The guy who log into the machine has his og her own profile (google account), so it is very easy to share a CB.
Im pretty sure that only the first who log into a google account will receive the free storage.
No Chromebook have issues with Netflix.
I'd go for the Samsung. But maybe the Lenovo will be a good alternative. The Acer is to noicy.
You can easily work off-line on a Chromebook with the stuff you have in your Drive. You'll, hence, not be that dependent on wifi. My CB has 3G which is another option to secure workflow no mater where you are.
You can check out other discussion group as forinstance the G+ community ChromebookEDU (its a great site where you'll get well informed about Chromebook).